Semi-direct products involving Sp_(2n) or Spin_n with free algebras of symmetric invariants

This is a part of an ongoing project, the goal of which is to classify all semi-direct products $\mathfrak s=\mathfrak g{\ltimes} V$ such that $\mathfrak g$ is a simple Lie algebra, $V$ is a $\mathfrak g$-module, and $\mathfrak s$ has a free algebra of symmetric invariants. In this paper, we obtain such a classification for the representations of the orthogonal and symplectic algebras.